RendervisStair Calculator
Calculate riser height, tread depth, number of steps, and stair angle from total height and available run.
Results
Stair diagram
Disclaimer: This calculator is a planning aid only. Always check local building codes and regulations for stair requirements in your jurisdiction.
How Stair Calculations Work
The calculator divides the total floor-to-floor height by a comfortable riser height (~18 cm / 7 in) to determine the number of risers. The available horizontal run is then divided by the number of treads (risers − 1) to find the tread depth.
Key Stair Measurements
| Measurement | Typical Range (Metric) | Typical Range (Imperial) |
|---|---|---|
| Riser height | 15–20 cm | 6–8 in |
| Tread depth | 25–30 cm | 10–12 in |
| Stair width (min) | 80–90 cm | 32–36 in |
| Comfortable angle | 30°–37° | |
Example
A floor-to-floor height of 280 cm with 400 cm of horizontal run gives approximately 16 risers at 17.5 cm each, with 15 treads at 26.7 cm each and a 35° angle.
Frequently Asked Questions
- What is a comfortable riser height?
- Most building codes recommend a riser height between 15–20 cm (6–8 inches). The most comfortable range is typically 17–19 cm (6.7–7.5 inches).
- What is the ideal stair angle?
- Comfortable residential stairs are typically between 30° and 37°. Steeper than 42° becomes uncomfortable and may violate building codes.
- How do I calculate the number of steps?
- Divide the total floor-to-floor height by your target riser height (typically 18 cm). Round to the nearest whole number, then divide the total height by that number for the exact riser height.
- What is the 2R + T rule?
- The "2R + T" rule states that two times the riser height plus the tread depth should equal 60–65 cm (24–25 inches). This provides a comfortable walking rhythm.
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